The present disclosure relates to a power transmission device, and particularly relates to a power transmission device that is mounted on a vehicle and provided with a transmission having a plurality of engagement elements for transmitting power from a motor to an axle, a case that accommodates the transmission, and a hydraulic control device that controls hydraulic pressure to the plurality of engagement elements.
There has been proposed a power transmission device of this type that is mounted on a vehicle and includes an automatic transmission having a plurality of clutches; a hydraulic circuit serving as an actuator that drives the plurality of clutches; and a mechanical oil pump that is driven by power from the engine, suctions hydraulic oil from an oil pan via a strainer, and supplies the hydraulic oil to the hydraulic circuit; and an electromagnetic pump that is driven by the electromagnetic force and suctions the hydraulic oil from an oil passage between the strainer and the mechanical oil pump to be able to supply the hydraulic oil to a clutch to be engaged when starting the vehicle (see, for example, Japanese Patent Application Publication No. 2010-164178). In this device, while the engine has automatically stopped, hydraulic pressure is applied to the clutch for starting the vehicle from the electromagnetic pump instead of a linear solenoid valve of the hydraulic circuit. Thus, the clutch can be quickly engaged by the linear solenoid valve immediately after a subsequent automatic start of the engine, and the vehicle can smoothly start.